The Iron Bearing Rocks of Minnesota — Winchell. 279 



may fairly be considered the most wonderful mine in the world. 



It has only forty acres and works but a small part of that. 

 It is only fifteen months since the first work was done on the 

 wooded hillside, now covered by shaft houses, hoisting machinery 

 and railroad tracks. And in that short space of time nearly 

 300,000 tons of iron ore have been mined and shipped by rail to 

 Two Harbors, and thence by boat to Cleveland and other points. 



Considering the area covered by the mine, this is a record 

 never before equaled, and chief credit is due to the superintendent 

 and general manager, Capt. Joseph Sell wood of Duluth, who has 

 put into operation a very simple but efficient method of mining 

 rapidly and cheaply. 



The next formation which contains workable deposits of iron 

 ore is the Huronian, which lies unconformably upon upturned 

 edges of the Keewatin. In this formation we find sedimentary 

 slates and quartzites interbedded with some gabbro and green- 

 stone. 



In the vicinity of Gunflint lake, on the international bound- 

 ary, this formation is found to contain deposits of granular, shiny 

 magnetite, more or less mixed with quartz and olivine. Hematite 

 ore is found in this same formation in connection with the red and 

 gray quartzyte of Pokegama Falls near Grand Rapids, on the Mis- 

 sissippi river above Aitkin. At this locality is the most western 

 outcrop of iron ore-bearing strata in the state. 



In this same Huronian formation are situated some of the 

 mines of northern Wisconsin and Michigan. The Penokee-Goge- 

 bic range is composed of rocks of this age. We may therefore 

 confidently expect to find profitable deposits of ore in this state in 

 many places where it is now unlooked for and unexpected. 



This ore is more regular in its manner of deposition than that 

 of the Keewatin. It is in beds interstratified with quartzite, all 

 having a general dip in this state of perhaps fifteen degrees to the 

 southeast. This quartzite is supposed to be the upper part of the 

 Huronian and to lie unconformably on the slates beneath. 



Next in order above the Huronian is found the gabbro, which 

 has been erupted and has flowed over the top of the Huronian 

 strata, in some places entirely concealing them from sight, bury- 

 ing them under 200 or 300 feet of gray igneous rock, and in others, 

 breaking up the Huronian quartzites and surrounding masses in 

 areas a half mile or more in extent. 



